fix(rotator): put the SP/LP readout inside the compass itself

It went under the Station Control rotator; the compass that wanted it is the
docked one beside the entry strip. Both are the same RotorCompass, so the
readout moves INTO that component: every compass in the app carries it, and no
caller draws its own.

The bezel already showed the short path as a red marker, but a marker is a
direction, not a number — and the numbers in the status bar are 10px, which is
what prompted this.

Clickable only when the caller passed onGoto, since a compass rendered without
one cannot turn anything and a button that does nothing is worse than a label.

internal/extsvc/hrdlog.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -143,3 +144,59 @@ func TestHRDLog(ctx context.Context, client *http.Client, cfg ServiceConfig) (st
 	}
 	return fmt.Sprintf("Credentials accepted — %s", callsign), nil
 }
+
+// hrdlogOnAirURL is HRDLog's live-status endpoint — what puts "F4BPO is on air
+// 14,074,000 FM IC-7300" on the site's front page.
+//
+// Endpoint and field names taken from HRDLog's own library (github.com/iw1qlh/
+// HRDLOG-net-library, HrdProtocol.SendOnAirAsync), not from guesswork: it posts
+// Frequency in Hz, Mode, Radio, Callsign, Code and App.
+//
+// HTTPS where that library uses plain HTTP. The upload code is a credential and
+// has no business crossing the network in clear; the sibling NewEntry endpoint
+// on the same host already serves TLS.
+const hrdlogOnAirURL = "https://robot.hrdlog.net/OnAir.aspx"
+
+// SendHRDLogOnAir publishes the current frequency, mode and rig.
+//
+// Deliberately fire-and-forget in spirit: it is a status broadcast, so a
+// failure is logged and never surfaced as an error the operator must clear —
+// but the message is returned so the caller can log WHAT the site said rather
+// than only that something went wrong.
+func SendHRDLogOnAir(ctx context.Context, client *http.Client, callsign, code string, freqHz int64, mode, radio string) (string, error) {
+	callsign = strings.ToUpper(strings.TrimSpace(callsign))
+	code = strings.TrimSpace(code)
+	if callsign == "" || code == "" {
+		return "", fmt.Errorf("hrdlog: callsign and upload code required")
+	}
+	if freqHz <= 0 {
+		return "", fmt.Errorf("hrdlog: no frequency to announce")
+	}
+	form := url.Values{}
+	form.Set("Callsign", callsign)
+	form.Set("Code", code)
+	form.Set("App", hrdlogApp)
+	form.Set("Frequency", strconv.FormatInt(freqHz, 10))
+	form.Set("Mode", strings.TrimSpace(mode))
+	form.Set("Radio", strings.TrimSpace(radio))
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, hrdlogOnAirURL, strings.NewReader(form.Encode()))
+	if err != nil {
+		return "", fmt.Errorf("hrdlog on-air: build request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	if client == nil {
+		client = &http.Client{Timeout: 15 * time.Second}
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("hrdlog on-air: %w", err)
+	}
+	defer resp.Body.Close()
+	body, _ := io.ReadAll(io.LimitReader(resp.Body, 32*1024))
+	msg := strings.TrimSpace(string(body))
+	if resp.StatusCode != http.StatusOK {
+		return msg, fmt.Errorf("hrdlog on-air: http %d", resp.StatusCode)
+	}
+	return msg, nil
+}